Mathematical model of radiation-induced shape change in fuel subassemblies of the BN-type reactor core and its implementation in ANSYS software package

Abstract

One of main operability criteria for fuel subassemblies (FSAs) in fast sodium reactor cores, i.e. the criterion of tolerable shape change in hexagonal wrapper tube is formulated. The equations which enable one to inquire into kinetics of the stress-strained state of a three-dimensional body are adapted to FSAs operating conditions. A mathematical model of radiation-induced shape change in ferritic-martensitic steel of grade EP-450 is proposed. With regard to the proposed model and data on the radiation-induced shape change in other current and prospective structural materials of BN reactor cores, blocks for recording of radiation-induced swelling and radiation-induced creep are developed for ANSYS software package, which made it possible to utilize its potentials within this area of focus. The performed test case with proposed models of the radiation-induced swelling and radiation-induced creep demonstrates that the developed blocks sufficiently describe the radiation-induced shape change in the examined structural materials exposed to radiation. A calculation of the radiation-induced shape change in the FSA hexagonal wrapper tube with various speeds of the radiation-induced swelling and the radiation-induced creep moduli is performed. The calculations results and the results of FSAs post-irradiation dimension inspection are compared. Recommendations for use of the proposed models aimed at performing calculations, as well as estimating the radiation-induced shape change and defining the stress-strained state of FSAs are made.